In a conventional method, a repairing operation at an interior of a tubular frame in a reactor vessel has to be operated in a underwater condition since the interior of the reactor vessel is filled with cooling water in an ordinary state.
However, in the case that a repairing operation is done in such an underwater condition, the all devices have to have a water-proof performance. The all devices become large and heavy. As the result, the all devices are treated with some difficulty.
The devices utilized in the underwater condition have to be decontaminated after lighting from the cooling water since those devices are exposed with radiation in the cooling water.
Recently, it is recommended a method for inspecting in an interior of tubular frame in the reactor vessel in an air environment (Patent Document 1).
In the recommended method, a water surface level of a cooling water at an interior of a reactor vessel is lowered with respect to a location of a tubular frame, a frame is set at an interior of the reactor vessel. At the interior of the frame, an operator inserts an Ultrasonic Testing (hereinafter, it is referred as “UT”) device for testing with ultrasonic wave into the tubular frame and sets it in the tubular frame so as to operate UT inspection.